.338 Lapua Magnum
The .338 Lapua Magnum (8.6×70mm or 8.58×70mm) is a specialized rimless bottlenecked centerfire cartridge developed for military long-range sniper rifles. The Afghanistan War and Iraq War made it a combat-proven round with ready and substantial ammunition availability. The .338 Lapua is a dual-purpose anti-personnel and anti-materiel round, but its anti-materiel potential is limited, due to the bullet's lower kinetic energy compared with that of the .50 BMG's 35.64-to-55.08-gram (550.0 to 850.0 gr) projectiles. The loaded cartridge is 14.93 mm (0.588 in) in diameter (rim) and 93.5 mm (3.68 in) long. It can penetrate better-than-standard military body armour at ranges up to 1,000 metres (1,094 yd) and has a maximum effective range of about 1,750 metres (1,910 yd). Muzzle velocity is dependent on load and powder temperature and varies from 880 to 915 m/s (2,900 to 3,000 ft/s) for commercial loads with 16.2-gram (250 gr) bullets, which results in about 6,525 J (4,813 ft·lbf) of muzzle energy. Non-C.I.P. conforming British military issue overpressure .338 Lapua Magnum cartridges with a 91.4 mm (3.60 in) overall length, loaded with 16.2-gram (250 gr) LockBase B408 very-low-drag bullets were used in November 2009 by British sniper Corporal of Horse (CoH) Craig Harrison to establish a new record for the longest confirmed sniper kill in combat, at a range of 2,475 m (2,707 yd). In addition to its military role, it is increasingly used by hunters and civilian long-range shooting enthusiasts. The .338 Lapua Magnum is capable of taking down any game animal, though its suitability for some dangerous game (Cape buffalo, hippopotamus, white rhinoceros and elephant) is arguable, unless accompanied by a larger "backup" caliber: "There is a huge difference between calibers that will kill an elephant and those that can be relied upon to stop one." History Initial development In 1983, Research Armament Industries (RAI) in the United States began development of a new, long-range sniper cartridge capable of firing a 16.2-gram (250 gr), 0.338-inch (8.6 mm) diameter bullet at 914 metres per second (3,000 ft/s) that could penetrate five layers of military body armour at 1,000 m (1,094 yd) and still make the kill. After preliminary experiments, a .416 Rigby case necked down to take a 0.338-inch (8.6 mm) bullet was selected, since this diameter presents an optimum of sectional density and penetrating capability for practical spin stabilized rifle bullets (bullets up to about 5 to 5.5 calibers in length). The .416 Rigby is an English big game cartridge that was designed to accommodate 325 MPa (47,137 psi) pressures. One of the disadvantages of these old cartridge cases, which were intended for firing cordite charges instead of modern smokeless powder, is the thickness of the sidewall just forward of the web. During ignition, the cartridge's base, forward to the bolt face, is not supported. The case is driven back against the bolt face which results in the stretching of the case, particularly the sidewall immediately forward of the web. When the sidewall resists the outward expansion against the chamber, the pressure stretches the case thereby increasing its length resulting in the sidewall becoming thinner at that stretch point. During the process RAI employed Brass Extrusion Labs Ltd. (BELL) of Bensenville, Illinois, to make the .338/416 or 8.58×71mm cartridge cases, Hornady produced bullets, and RAI built a sniper rifle under contract for the U.S. Navy. RAI found that the BELL cases did not fulfill the requirements. Pressed by military deadlines RAI looked for another case producer and contacted Lapua of Finland in 1984. RAI was forced to drop out of the program due to financial difficulties. Subsequently, Lapua of Finland put this cartridge into limited production. The .338/416 rifle program was later cancelled when the contractors were unable to make the cartridge meet the project's velocity target 16.2 gram at 914 m/s (250 gr at 3000 ft/s), due to weak brass cases. Final development The current .338 Lapua Magnum cartridge was developed as a joint venture between the Finnish rifle manufacturer SAKO and the British rifle manufacturer Accuracy International along with the Finnish ammunition manufacturer Lapua, or more officially Nammo Lapua Oy, which since 1998 is part of the Nordic Ammunition Group (Nammo). Lapua opted to redesign the .338/416 cartridge. In the new case design, particular attention was directed toward thickening and metallurgically strengthening the case's web and sidewall immediately forward of the web. In modern solid head cases, the hardness of the brass is the major factor that determines a case's pressure limit before undergoing plastic deformation. Lapua tackled this problem by creating a hardness distribution ranging from the head and web (hard) to the mouth (soft) as well as a strengthened (thicker) case web and sidewall immediately forward of the web. This resulted in a very pressure resistant case, allowing it to operate at high pressure and come within 15 m/s (50 ft/s) of the original velocity goal. Lapua also designed a 16.2-gram (250 gr) .338 calibre Lock Base B408 full metal jacket bullet, modeled after its .30 calibre Lock Base bullet configuration. The result was the .338 Lapua Magnum cartridge which was registered with C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) in 1989. With the procurement by the Dutch Army, the cartridge became NATO codified. The .338 Lapua Magnum fills the gap between weapons chambered for standard military rounds such as the 7.62x51mm NATO and large, weighty rifles firing the .50 BMG cartridge. It also offers a tolerable amount of barrel wear, which is important to military snipers who tend to fire thousands of rounds in practice every year to acquire and maintain expert long-range marksmanship. Like every other comparable big magnum rifle cartridge the .338 Lapua Magnum presents a stout recoil. An appropriate fitting stock and an effective muzzle brake will help to reduce recoil induced problems, enabling the operator to fire more rounds before getting too uncomfortable to shoot accurately. Good factory loads, multiple projectile weights and factory special application ammunition are all available. Due to its growing civilian popularity, several high quality tactical and match (semi) custom bolt actions designed for the .338 Lapua Magnum are becoming available. These (semi) custom bolt actions are used with other high grade rifle and sighting components to build custom sporting and target rifles. Supersonic range performance of the .338 Lapua Magnum Performance with C.I.P. conform cartridges For a typical .338 Lapua Magnum high end factory military sniper rifle like the Sako TRG-42 with a 690 mm (27.2 in) long 305 mm (1 in 12 inch) rifling twist rate barrel at sea level, 1,500 m (1,640 yd) is considered to be the maximum shooting distance for man sized targets. When using standard Lapua military 16.2 g (250 gr) loads it has a supersonic range of 1,500 m (1,640 yd) under warm summer conditions at a muzzle velocity of 915 m/s (3,000 ft/s). However, to be able to maintain 80 to 90% hit probability on non-moving 45 cm × 90 cm (17.7 in × 35.4 in) reactive army targets, this maximum shooting distance has to be reduced to 1,300 metres (1,422 yd) at freezing point conditions or 1,100 m (1,203 yd) in Arctic winter conditions, when the muzzle velocity may drop to 880 m/s (2,887 ft/s)—i.e. only during optimal warm summer conditions the 1,500 m (1,640 yd) maximum shooting distance is realistically achievable. Loaded with more aerodynamic very-low-drag bullets such as the traditionally lead cored 19.44 g (300.0 gr) Lapua Scenar GB528 VLD bullet (G1 BC = 0.736) or the Lost River Ballistics J40 .338 17.5 gram (270 gr) CNC manufactured mono-metal bullet (G1 BC = 0.871) the long-range performance and supersonic range of .338 Lapua Magnum rifles can be improved. These longer very-low-drag bullets require a 254 mm (1 in 10 inch) twist rate to stabilize them. Due to the lower practically possible muzzle velocities for a relative heavy bullet like the 19.44 g (300 gr) Lapua Scenar GB528 VLD bullet it gains about 104 m (114 yd) extra supersonic range under International Standard Atmosphere sea level conditions (air density ρ = 1.225 kg/m3) at a muzzle velocity of 837 m/s (2750 ft/s) when compared to the standard 16.2 g (250 gr) Lapua Scenar GB488 VLD at a muzzle velocity of 915 m/s (3002 ft/s). For significant supersonic range improvement the aerodynamic efficiency of the employed bullets has to be significantly improved without sacrificing a lot of practically achievable muzzle velocity - meaning that besides the coefficient of drag of the projectile weight is also an important parameter for its actual downrange flight behavior. The .338 17.5 gram (270 gr) Lost River Ballistic Technologies J40 match bullet made out of a copper-nickel alloy is one of the most aerodynamic .338 calibre bullets available. It has a 1800 m (1969 yd) supersonic range under optimal warm summer conditions at a muzzle velocity of 869 m/s (2850 ft/s). This makes engaging static targets up to 1800 m (1969 yd) feasible. Performance improvement experiments with non C.I.P. conform cartridges Improvement beyond this standard while still using standard .338 Lapua Magnum brass is possible, but the bullets have to be very long (over 5.5 calibers in length) and the normal cartridge overall length of 93.5 mm has to be exceeded making such cartridges wildcats. The common 254 mm (1:10 inch) rifling twist rate also has to be tightened to stabilize very long projectiles. Such commercially non-existent cartridges are termed "wildcats". The use of a wildcat .338 Lapua Magnum based cartridge demands the use of a custom or customized rifle with an appropriately cut chamber and fast-twist bore. The firearm action and if a repeating arm is required the magazine(s) must also be able to cope with dimensional increases. An example of such a special .338 calibre extreme range bullet is the German CNC manufactured mono-metal 18.92 gram (292 gr) LM-105 (G1 BC ≈ 0.93 – this Ballistic coefficient (BC) is calculated by its designer, Lutz Möller, and not proven by Doppler radar measurements). If Möller's assumptions are correct, the LM-105 would have a supersonic range of ≈ 2000 m (2200 yd) at a muzzle velocity of 915 m/s (3,002 ft/s) under International Standard Atmosphere sea level conditions (air density ρ = 1.225 kg/m3). The 2010 version of the LM-105 bullet has an overall length of 54.3 mm (2.14 in) or 6.33 calibers and derives its exceptional low drag from a radical LD Haack or Sears-Haack profile in the bullet's nose area. Rifles chambered for this wildcat cartridge, with a cartridge overall length of 105 mm (4.13 in), and equipped with custom made 178 mm (1:7 inch) progressive twist rate 900 mm (35.43 in) long barrels with a 2° cone-angle (the standard C.I.P. cone-angle for the .338 Lapua Magnum is 6°) cone area finished first and second at several long range competitions. Its most recent win (2007) was in an international Special Forces and police sniper competition in Switzerland against rifles chambered for 7.62×51mm NATO up to .50 BMG at ranges from 100 m – 1,500 m (109 yd – 1,640 yd). The LM-105 bullet exhibited its very low wind drift susceptibility notably at ranges beyond 800 m (875 yd). A real world average G1 BC of ≈ 0.90 to 0.93 is commonly adopted by the users of this bullet, for making long range trajectory predictions using ballistics calculators.[60] The .343 Lapua Magnum LM-107 was a wildcat cartridge under development based on the standard .338 Lapua Magnum cartridge case. The LM-107 was hoped to boost the ballistic performance of the LM-105 by achieving an increase in supersonic range. The 19.3 g (298 gr) LM-107 projectile design is 59 mm long and has a Haack profiled nose and an Adams profiled tail. The rifling twist rate for the .343 Lapua Magnum LM-107 wildcat cartridge was chosen at 180 mm (1:7 inch), Ø lands = 8.72 mm, Ø grooves = 8.45 mm and loaded with the LM-107 projectile has a cartridge overall length of 107 mm. The length of the neck is increased from 8,31 to 8,50 mm to support the bigger LM-107 bullet. Several other dimensions of the .338 Lapua Magnum parental cartridge are also changed. The shoulder angle gets steepened from 40° to 60° and the body taper is set at 1°. The throat area is set at a 2° cone-angle. All this modifications make the .343 Lapua Magnum a fairly comprehensively revised wildcat cartridge. Out of a 900 mm (35.43 in) long progressive twist barrel Mr. Möller expected to achieve 909 m/s (2982 ft/s) muzzle velocity. If Möller's design assumptions are correct the LM-107 projectile with a calculated G1 BC of 1.02 will offer a supersonic range of ≈ 2170 m (2373 yd) at a muzzle velocity of 909 m/s (2982 ft/s) under International Standard Atmosphere sea level conditions (air density ρ = 1.225 kg/m3). Category:Weapons